1. Field of the Invention
The present invention relates to fuel and lubricant additives based on long-chain hydrocarbon radicals having a polar terminal group, a halogen-free, one-stage process for the preparation of these additives, in which polar reactants are subjected to a free radical addition reaction at the double bond of a long-chain olefin, and fuel and lubricant compositions which contain these additives.
2. Discussion of the Background
Carburettors and intake systems of gasoline engines as well as injection systems for metering fuel in gasoline and diesel engines are increasingly being contaminated by impurities which are caused by dust particles from the air, uncombusted hydrocarbon residues from the combustion chamber and crank case vent gases passed into the carburettor.
These residues shift the air/fuel ratio during idling and in the lower part-load range so that the mixture becomes richer, the combustion becomes more incomplete and in turn the proportions of uncombusted or partly combusted hydrocarbons in the exhaust gas becomes larger and the gasoline consumption rises.
It is known that, in order to avoid these disadvantages, fuel additives are used for keeping valves and carburettors or injection systems clean (cf. for example: M. Rossenbeck in Katalysatoren, Tenside, Mineraloladditive, ed. J. Falbe and U. Hasserodt, page 223, G. Thieme Verlag, Stuttgart 1978).
Depending on the mode of action as well as on the preferred place of action of such detergent additives, a distinction is made today between two generations.
The first generation of additives was capable only of preventing the formation of deposits in the intake system but not of removing existing deposits, whereas the modern additives of the second generation can achieve both (keep-clean and clean-up effect), and can do so in particular because of their excellent heat stability in zones at relatively high temperature, ie. in the intake valves.
The molecular structural principle of these additives which act as detergents can be stated in general to be a linkage of polar structures with mostly high molecular weight, nonpolar or oleophilic radicals.
Members of the second generation of additives are often products based on polyisobutene in the nonpolar moiety. Here too, additives of the polyisobutylamine type are particularly noteworthy.
Such detergents are obtained, starting from polyisobutenes, essentially by two multistage synthesis processes.
The first involves chlorination of the polymeric parent structure, followed by nucleophilic substitution of the polymeric parent structure by amines or, preferably, ammonia. A disadvantage of this process, apart from the two-stage nature of the synthesis, is the use of chlorine which results in the occurrence of chlorine- or chloride-containing products, which is no longer desirable today.
In the second process, polyisobutylamines are obtained from polyisobutene by hydroformylation, followed by reductive amination, ie. once again a two-stage process which also requires an appropriate infrastructure.
Simple, one-stage, chlorine-free synthesis processes for detergents and dispersants or compounds which combine both property profiles, which can be carried out in standard apparatuses, are therefore of particular technical and economic interest.
GB-A-1,383,423 discloses a method for the preparation of alkylpolyamines which can be used as carburettor detergents. Here, an .alpha.-olefin of at least 15 carbon atoms is reacted with a polyamine in the presence of a free radical initiator. The .alpha.-olefins used are particularly preferably polyisobutylenes.
EP-B-0 342 792 describes a process for the preparation of a polybutene having a thioether function, in which an organic thiol is reacted with a liquid polybutene which has one carbon-carbon double bond per molecule and a number average molecular weight of from 200 to 10,000 under conditions in which free radicals are produced.